JP5564303B2 - X-ray transmission inspection equipment - Google Patents

Description

  The present invention relates to an X-ray transmission inspection apparatus and an X-ray transmission inspection method capable of detecting a foreign substance made of a specific element in a sample.

  In recent years, lithium ion secondary batteries having higher energy density than nickel metal hydride batteries are being adopted as batteries for automobiles, hybrid cars, electric cars and the like. This lithium ion secondary battery is a kind of non-aqueous electrolyte secondary battery, which is a secondary battery in which the lithium ion in the electrolyte is responsible for electrical conduction and does not contain metallic lithium in the battery. Many telephones have already been adopted.

  Although this lithium ion secondary battery has excellent battery characteristics, reliability such as deterioration of battery characteristics such as heat generation and life when foreign matter such as Fe (iron) enters the electrode during the manufacturing process Until now, it has been delayed for in-vehicle use. For example, as shown in FIG. 4 (a), the lithium ion secondary battery electrode (positive electrode) has a lithium cobalt oxide film or a lithium manganese oxide film 2 of about 100 μm formed on both surfaces of an Al film 1 having a thickness of 20 μm. However, as shown in FIG. 4 (b), foreign matter X of Fe (iron) or SUS (stainless steel) may be mixed in this, and the foreign matter X is several tens of μm or more. If so, a short circuit can occur, which can cause the battery to burn out or degrade performance. For this reason, about a lithium ion secondary battery, it is calculated | required that a battery in which the foreign material X was mixed at the time of manufacture is detected rapidly by inspection, and removed beforehand.

  Generally, a method using a transmission X-ray image is known as a method for detecting a foreign substance or the like in a sample. A carbonaceous material foreign matter detection method for detecting the presence or absence of foreign matter in a carbon-based material or the like used as a negative electrode of a lithium ion secondary battery by using a transmission X-ray image has been proposed using this technique ( Patent Document 1).

Japanese Patent Laying-Open No. 2004-239776 (Claims)

  The following problems remain in the conventional technology.

  That is, in the conventional foreign matter detection method, since the presence or absence of foreign matter is simply detected based on the intensity of the transmitted X-ray image, a clear contrast can be obtained if the atomic number of the foreign matter is greatly different. There is a problem that contrast is weak and difficult to discriminate. For example, the same applies to Co (atomic number 27) included as one of the constituent elements in the electrode (positive electrode plate) serving as the measurement sample and Fe (atomic number 26) of the element constituting the foreign matter to be detected. Contrast. For this reason, in the conventional foreign matter detection method, as shown in FIG. 4A, for example, in the transmission X-ray image T of the electrode (positive electrode plate) that is the measurement sample S, the component 2 is locally thick in the portion 2a. As shown in FIG. 4B, there is a problem in that it is not possible to determine whether the contrast is caused by the contrast due to the foreign object X, and excessive detection or erroneous detection occurs.

  The present invention has been made in view of the above-described problems, and provides an X-ray transmission inspection apparatus and an X-ray transmission inspection method that can clearly discriminate only the contrast caused by a foreign substance and prevent overdetection and erroneous detection. For the purpose.

  The present invention employs the following configuration in order to solve the above problems. That is, in the X-ray transmission inspection apparatus and the X-ray transmission inspection method of the present invention, an element that is lower than the X-ray absorption edge of one element contained in the measurement sample and is a detection target (hereinafter referred to as “detection element”). ) Irradiates the measurement sample with characteristic X-rays with energy higher than the X-ray absorption edge, receives the transmitted X-rays when the characteristic X-rays pass through the measurement sample, and detects the intensity with an X-ray detector. A contrast image is obtained by calculating from a transmission image showing the distribution of the detected intensity of the transmitted X-rays.

  In addition, the characteristic X-rays irradiated to the measurement sample are formed of an element having an X-ray absorption edge of energy between the Kα-rays of the characteristic X-rays and the Kβ-rays for removing the Kβ-rays of the characteristic X-rays. Use a filter.

  In these X-ray transmission inspection apparatuses and X-ray transmission inspection methods, the characteristic X-rays are monochromatized with energy lower than the X-ray absorption edge of one element contained in the measurement sample and higher than the X-ray absorption edge of the detection element. Since the sample is irradiated to obtain a transmission image, a clear contrast image of a specific element can be obtained. In other words, it is possible to measure even if there are other elements with similar atomic numbers by using high-energy monochromatic X-rays at the X-ray absorption edge of the above elements instead of X-rays mixed with various energies such as white X-rays. A clear contrast image of the target element can be obtained.

  Furthermore, since a filter formed of an element having an X-ray absorption edge of energy between the Kα ray and Kβ ray of the characteristic X-ray is arranged between the measurement sample and the X-ray tube, Of the characteristic X-rays, Kβ rays can be cut by a filter. Therefore, since only the desired characteristic X-rays are extracted and the sample can be irradiated, the contrast of the element to be measured becomes clearer.

  In the X-ray transmission inspection apparatus according to the present invention, the measurement sample contains lithium cobalt oxide, the X-ray tube is a Ni target tube, the detection element is Fe, and the filter is a Co foil. It is characterized by being.

  That is, the X-ray transmission inspection apparatus of the present invention uses lithium cobaltate as a representative sample, and uses lithium cobaltate as a measurement sample to detect foreign matters mainly containing Fe in the measurement sample. As a characteristic X-ray having an energy lower than the X-ray absorption edge (7.709 keV) of Co, which is one constituent element, and higher than the X-ray absorption edge (7.111 keV) of Fe, which is the detection element, a Ni target tube A characteristic X-ray (7.477 keV) of Ni by a sphere is used. Thereby, Fe can be detected with a clear contrast image using an inexpensive X-ray tube.

  In addition, the X-ray transmission inspection apparatus extracts only Ni-Kα characteristic X-rays (7.477 keV) using a Co (X-ray absorption edge = 7.709 keV) foil filter and irradiates the measurement sample. Can do.

  In the X-ray transmission inspection apparatus of the present invention, the measurement sample contains lithium manganate, the X-ray tube is a Fe target tube, the detection element is Cr, and the filter is a Mn foil. It is characterized by being.

  That is, the X-ray transmission inspection apparatus according to the present invention uses lithium manganate as a representative measurement material, and in the case of detecting foreign matters mainly containing Cr in the measurement sample, Fe target tube as a characteristic X-ray having an energy lower than the X-ray absorption edge (6.540 keV) of Mn, which is one constituent element, and higher than the X-ray absorption edge (5.989 keV) of Cr, which is the detection element A characteristic X-ray (6.403 keV) of Fe by a sphere is used. Thereby, Cr can be detected with a clear contrast image using an inexpensive X-ray tube.

  In addition, the X-ray transmission inspection apparatus extracts only the Fe-Kα characteristic X-ray (6.403 keV) using a filter of Mn (X-ray absorption edge = 6.540 keV) foil and irradiates the measurement sample. Can do.

  The present invention has the following effects.

  That is, according to the X-ray transmission inspection apparatus and the X-ray transmission inspection method according to the present invention, the energy is lower than the X-ray absorption edge of one element contained in the measurement sample and higher than the X-ray absorption edge of the detection element. Since a contrast image is obtained from a transmission image obtained by irradiating the sample with characteristic X-rays, a clear contrast image can be obtained for a specific element to be detected. Furthermore, since a filter formed of an element having an X-ray absorption edge of energy between the Kα ray and the Kβ ray of the characteristic X ray by the X-ray tube is arranged between the sample and the X-ray tube, Only desired characteristic X-rays (Kα rays) can be extracted and irradiated, and the contrast of the detection element to be measured can be acquired more clearly even in the presence of an element having an atomic number close to that of the target element.

  Therefore, by using this X-ray transmission inspection apparatus and X-ray transmission inspection method, it is possible to detect a foreign substance of a specific element in a lithium ion secondary battery or the like with high accuracy and speed.

1 is a schematic overall configuration diagram showing an embodiment of an X-ray transmission inspection apparatus and an X-ray transmission inspection method according to the present invention. It is a figure which shows the relationship between the energy of X-ray | X_line in the embodiment of this invention, and the transmittance | permeability of X-ray | X_line. (A) It is explanatory drawing which shows the transmitted image of X-ray in the case of including the part from which thickness differs locally at the time of X-ray transmission of embodiment of this invention. (B) It is explanatory drawing which shows the transmitted image of X-ray in the case of containing a foreign material in the surface layer at the time of X-ray transmission of embodiment of this invention. (A) It is explanatory drawing which shows the transmitted image of X-ray in the case of including the part from which thickness differs locally at the time of the conventional X-ray transmission. (B) It is explanatory drawing which shows the transmitted image of X-ray in the case of containing a foreign material in the surface layer at the time of the conventional X-ray transmission.

  Hereinafter, an embodiment of an X-ray transmission inspection apparatus and an X-ray transmission inspection method according to the present invention will be described with reference to FIGS. 1 to 3.

  As shown in FIG. 1, the X-ray transmission inspection apparatus of this embodiment is an X-ray having energy lower than the X-ray absorption edge of one element included in the measurement sample S and higher than the X-ray absorption edge of the detection element. X-ray tube 11 that irradiates measurement sample S, X-ray detector 13 that receives the transmitted X-ray when X-rays pass through measurement sample S and detects the intensity thereof, and the detected transmitted X-ray A display unit 18 for displaying a transmission image showing the intensity distribution is provided.

  The X-ray transmission inspection apparatus includes a belt conveyor 16 that is a sample stage on which a measurement sample S can be placed and moved in the horizontal direction, a control unit 17 that is connected to each of the above-described components and controls each of the components. And a display unit 18 connected to the unit 15 to display the contrast image and the like.

  Further, in the X-ray transmission inspection apparatus, an X-ray absorption end of energy between the Kα ray and the Kβ ray of the characteristic X ray from the X-ray tube is provided between the measurement sample S and the X-ray tube 11. A filter F1 formed of an element is arranged.

  The measurement sample S is, for example, an electrode used for a lithium ion secondary battery, and the detection element is, for example, Fe or Cr in SUS, which may be mixed into the electrode as a foreign substance.

  When the detection element is Fe, the X-ray tube 11 is a Ni tube having a Ni target. From the X-ray tube 11 of the Ni tube, for example, Ni-Kα characteristic X-rays (7.477 keV) are emitted as X-rays having higher energy than the K absorption edge (7.111 keV) of Fe.

  At this time, a Co foil is employed as the filter F1.

  When the detection element is Cr, the X-ray tube 11 is an Fe tube having an Fe target.

  From the X-ray tube 11 of the Fe tube, for example, Fe-Kα characteristic X-rays (6.403 keV) are emitted as X-rays having higher energy than the K absorption edge (5.988 keV) of Cr.

  At this time, a Mn foil is employed as the filter F1.

  In the case where the detection element is Fe or Cr, the characteristic X-ray energy that can be used as the X-ray and the energy of the X-ray absorption edge of the element that can be used as the filter F1 are shown in Table 1 as an example. .

  These X-ray tubes are generated by the collision of the thermoelectrons generated from the filament (anode) in the tube with the target by being accelerated by the voltage applied between the filament (anode) and the target (cathode). A line is emitted as a primary X-ray from a window such as beryllium foil.

  The X-ray detector 13 is an X-ray line sensor disposed below the belt conveyor 16 so as to face the corresponding X-ray tube 11. As this X-ray line sensor, a scintillator method in which X-rays are converted into fluorescence by a fluorescent plate and converted into a current signal by a light receiving element arranged in a row, a semiconductor method in which a plurality of semiconductor detection elements are arranged in a row, etc. are adopted. . These X-ray sensors may be X-ray area sensors in which light receiving elements are arranged two-dimensionally in addition to a single line.

  The control unit 17 is a computer configured with a CPU or the like.

  The calculation unit 15 performs image processing based on a signal from the X-ray detector 13 input via the control unit 17 to create a transmission image, and further displays the image on the display unit 18. Circuit etc. Note that a processing circuit of the calculation unit 15 may be provided in the control unit 17 so that both are integrated. The display unit 18 can display various information according to control from the control unit 17.

  Next, an X-ray transmission inspection method using the X-ray transmission inspection apparatus of this embodiment will be described with reference to FIGS. In this X-ray transmission inspection method, for example, the measurement sample S is a lithium cobalt oxide electrode, the foreign substance X contained therein is iron, the detection element is Fe, and the X-ray tube 11 is a Ni tube.

  First, the measurement sample S is moved to a position facing the X-ray tube 11 by the belt conveyor 16.

  Then, Ni-Kα characteristic X-rays are irradiated as X-rays from the X-ray tube 11 of the Ni tube to the measurement sample S, and transmitted X-rays transmitted through the measurement sample S are detected by the X-ray detector 13. At this time, the entire sample is scanned by moving the measurement sample S on the belt conveyor 16, and the entire intensity distribution of the transmitted X-ray is acquired.

  At this time, the X-ray (Ni-Kα characteristic X-ray = 7.477 keV) emitted from the X-ray tube 11 of the Ni tube is one of the constituent elements of the lithium cobalt oxide battery that is the measurement sample S. The energy is lower than the X-ray absorption edge (7.709 keV) of Co and higher than the X-ray absorption edge (7.112 keV) of the detection element Fe. Accordingly, the lithium cobaltate itself that is the measurement sample S is transmitted and is absorbed by the iron that is the foreign matter X, whereby a high contrast image is obtained. Furthermore, before irradiation of the measurement sample S, characteristic X-rays with higher energy than the X-ray absorption edge of Co (Ni-Kβ characteristic X-ray (8.264 keV), etc.) and background X-rays are The measurement sample S is irradiated with only approximately Ni-Kα characteristic X-rays (7.477 keV), which is cut by absorption by the filter F1.

  Here, “one element included in the measurement sample” means “in accordance with the present invention” “with an energy lower than the X-ray absorption edge of one element included in the measurement sample and higher than the X-ray absorption edge of the detection element. Elements that can be representative of the measurement sample are selected so that “irradiate the measurement sample with X-rays” is established. Therefore, in the case of this example, it is one of the constituent elements of the lithium cobalt oxide battery, and Co is determined from the relationship between the detection element and the X-ray.

  The calculation unit 15 performs image processing on the intensity distribution of the transmitted X-rays obtained in this way to create a transmission image.

  The X-ray transmittance for the lithium cobalt oxide electrode is, for example, 20 μm of Fe foreign matter compared to the case where no foreign matter is present, as shown in FIG. 2, the energy corresponding to the X-ray absorption edge of Fe. As a result, the X-ray transmittance decreases. Further, the Ni-Kα characteristic X-ray, which is an X-ray, has energy corresponding to the high energy of the X-ray absorption edge of Fe.

  For this reason, as shown in FIG. 3A, when the constituent material of the measurement sample S (the electrode material in which the lithium cobalt oxide film 2 is laminated on both surfaces of the Al film 1) has a locally thick portion 2a, In the transmission image T1 of the Ni tube bulb by the X-ray tube 11, a clear contrast does not appear in a portion corresponding to the locally thick portion 1a. Further, as shown in FIG. 3B, when the measurement sample S has a foreign substance X of Fe, a transmission image T1 of the Ni tube X by the X-ray tube 11 clearly shows a portion corresponding to the foreign substance X. Contrast is shown. That is, since the Ni-Kα characteristic X-ray having higher energy than the X-ray absorption edge of Fe has a lower X-ray transmittance with respect to the foreign matter X of Fe, the amount transmitted through the foreign matter X portion is transmitted through the other portions. The amount is lower than the amount to be dark, and a dark portion is produced, resulting in a contrast.

  In the above, the X-ray transmission inspection method for detecting the foreign matter X in the lithium cobalt oxide electrode is exemplified. However, the present invention is an manganic acid used for a positive electrode plate as an electrode material used for a lithium ion secondary battery. The present invention can be similarly applied to inspection of foreign matters in lithium and inspection of foreign matters in a laminated material of Al (aluminum) and C (graphite) used for the negative electrode plate.

  Regarding the X-ray transmittance for these materials, when there is a foreign substance X of Fe, the X-ray transmittance decreases at the X-ray absorption edge of Fe. Therefore, even when the foreign matter X in these materials is detected, X-rays having energy lower than the energy of the X-ray absorption edge of the main element constituting the material and located at high energy of the Fe X-ray absorption edge By using (for example, Ni-Kα characteristic X-rays from a Ni tube), a contrast image in which the foreign matter X portion is emphasized can be obtained.

  As described above, in the X-ray transmission inspection apparatus and the X-ray inspection method of this embodiment, X-rays having energy lower than the X-ray absorption edge of one element contained in the measurement sample and higher than the X-ray absorption edge of the detection element. Since a contrast image is obtained from the transmission image T1 obtained by irradiating the measurement sample S with a clear contrast image, a clear contrast image can be obtained for a specific detection element. That is, it is not an X-ray mixed with various energies such as white X-rays, but a characteristic X-ray that transmits the measurement sample itself and has an X-ray absorption edge on the high energy side of the X-ray absorption edge of the detection element. By irradiating characteristic X-rays that cause a difference in the detected amount of transmitted X-rays, it is possible to obtain a clear contrast image of the element to be measured even in the presence of another element with an atomic number approaching. It becomes possible.

  Further, a filter F1 formed between the measurement sample S and the X-ray tube 11 is formed of an element having an X-ray absorption edge of energy between the Kα ray and the Kβ ray of the characteristic X ray from the X-ray tube. Therefore, unnecessary radiation (not only characteristic X-rays from the X-ray tube 11 but also characteristic X-rays having higher energy than these and background X-rays) can be cut by the filter F1. Therefore, since only the desired characteristic X-rays are extracted and can be irradiated to the measurement sample S, the contrast of the element to be measured becomes clearer.

  Further, when the measurement sample includes lithium cobalt oxide, an X-ray tube 11 of a Ni tube capable of emitting characteristic X-rays of Ni positioned at high energy at the X-ray absorption edge of Fe when Fe is a detection element. , Fe foreign matter X can be detected with a clear contrast image by an inexpensive X-ray tube.

  Further, since the filter is a Co foil, only the Ni-Kα characteristic X-ray (7.477 keV) can be extracted by the Co X-ray absorption edge (7.709 keV). That is, the Ni-Kβ characteristic X-ray (8.264 keV) is cut by the X-ray absorption edge (7.709 keV) of Co.

  Further, when the measurement sample contains lithium manganate, an X-ray tube 11 of an Fe tube capable of emitting characteristic X-rays of Fe positioned at high energy at the X-ray absorption edge of Cr when Cr is used as a detection element. Can be used to detect a foreign substance X such as SUS containing Cr with a clear contrast image using an inexpensive X-ray tube.

  Further, when the X-ray tube 11 is an Fe tube, since the filter F1 is an Mn foil, only the Fe-Kα characteristic X-ray (6.403 keV) is extracted from the X-ray absorption edge (6.537 keV) of Mn. can do. That is, the Fe-Kβ characteristic X-ray (7.057 keV) is cut by the X-ray absorption edge (6.537 keV) of Mn.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 11 ... X-ray tube, 13 ... X-ray detector, 15 ... Operation part, 16 ... Belt conveyor, 17 ... Control part, 18 ... Display part, F1 ... Filter, S ... Measurement sample, T1 ... Transmission image, X ... Detection target (foreign matter)

Claims (4)

The electrode material is irradiated with characteristic X-rays having energy lower than the X-ray absorption edge of one element contained in the electrode material for a lithium ion secondary battery as a measurement sample and higher than the X-ray absorption edge of the detection element. An X-ray tube,
An X-ray detector that receives the transmitted X-ray when the characteristic X-ray passes through the electrode material and detects its intensity;
An arithmetic unit that obtains a contrast image from the detected transmission X-ray intensity distribution;
Between the X-ray tube and the electrode material, Bei example and a filter element comprising an X-ray absorption edge of energy between the Kα line and the Kβ line of the characteristic X-rays,
The electrode material contains lithium cobalt oxide,
The X-ray tube is a Ni target tube;
An X-ray transmission inspection apparatus, wherein the detection element is Fe . The X-ray transmission inspection apparatus according to claim 1, wherein the filter is a Co foil. The electrode material is irradiated with characteristic X-rays having energy lower than the X-ray absorption edge of one element contained in the electrode material for a lithium ion secondary battery as a measurement sample and higher than the X-ray absorption edge of the detection element. An X-ray tube,
An X-ray detector that receives the transmitted X-ray when the characteristic X-ray passes through the electrode material and detects its intensity;
An arithmetic unit that obtains a contrast image from the detected transmission X-ray intensity distribution;
A filter comprising an element which is an X-ray absorption edge of energy between the Kα ray and Kβ ray of the characteristic X-ray between the electrode material and the X-ray tube;
The electrode material contains lithium manganate;
The X-ray tube is an Fe target tube;
An X-ray transmission inspection apparatus, wherein the detection element is Cr. The X-ray transmission inspection apparatus according to claim 3 , wherein the filter is a Mn foil.

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